Steve Fossett flew over the Middle East, India and China on Thursday as he pushed on with his bid to make the longest non-stop flight in history.
Fossett is hoping for good tailwinds
The adventurer's Virgin GlobalFlyer was expected to clear Shanghai and make for the Pacific at about 2230 GMT.
It is understood his plane lost 4% of its fuel during takeoff from Florida.
Mission engineers say it will now be touch and go as to whether the aviator has sufficient reserves to make his planned landing in the UK on Saturday.
Sixty-one-year-old Fossett is aiming for Kent International Airport near London.
To get there, he will have had to travel around the world once and across the Atlantic twice.
But, if everything goes according to plan, the adventurer will eclipse the distance record set by Dick Rutan and Jeana Yeager, who logged 40,212km (24,987 miles) during a non-stop, non-refuelled trip around the globe in their Voyager aircraft in 1986.
Fossett's mission control believes GlobalFlyer lost some 340kg (750lbs) of fuel during takeoff from the Kennedy Space Center on Wednesday. The exact reason is not clear but it is believed to be the result of a venting problem on the fuel tanks.
His engineers say he is now trying to fly GlobalFlyer as efficiently as possible. This means flying slowly without losing too much altitude.
The team is also hoping he will encounter strong tailwinds to push him along.
"He's still got a lot of flying to do so we just have to do the best we can to advise him on how high and how fast to fly," Clint Nichols from Scaled Composites, the company which built the experimental aircraft, said in a statement.
"Steve has reported he's fine and that everything is working okay."
Richard Branson, the billionaire British entrepreneur and founder of Virgin Atlantic airlines which is backing Fossett's bid, was said to be optimistic, but had put his friend's record-breaking chances at "50-50".
Chief engineer John Karkow emphasised the uncertainty in the team: "I am neutral at this point - there is some pessimism and some optimism, it is going to be interesting the whole way round.
"I do not think we will really know until he touches down in Kent," he told the AFP news agency.